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SAFETY AND ARMING SYSTEM Filed March 29, 1961 HARVEY A. FOURE INVENTOR BY lg-fiotivmli aulp q- 1 g ijjnfiwaw United States Patent 3,125,958 SAFETY AND ARMING SYSTEM Harvey A. Foure, Landover, Md., assignor to the United States of America as represented by the Secretary of the Army Filed Mar. 29, 1961, Ser. No. 99,325

1 Claim. (Cl. 102-78) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates in general to a safety and arming system for use in ground-to-ground missiles. More specifically, this invention relates to a safety and arming system which arms the missile warhead a constant time after re-entry of the missile into the atmosphere.

In order to minimize the effect of enemy countermeasures which may be applied against the fuzing system of ground-to-ground missiles, it is important that arming not occur until the missile has almost reached the target. The shorter the time interval between arming and impact, the shorter the period of time during which countermeasures can be applied to prematurely explode the missile. Ground-to-ground missiles are ordinarily launched at a steep angle, leave the atmosphere, and thereafter reenter on their approach to the target. As the missile reenters the atmosphere, it usually is not travelling precisely nose-downwards towards the target. The missile will therefore generally oscillate for a short period of time about its center of gravity until it becomes aerodynarnically stable.

Since the point of reentry is necessarily close to the target area if the missile is on course, it is desirable that final arming occur a short period of time after reentry and before impact in order to minimize the effectiveness of enemy countermeasures.

Known prior art inertia arming systems which are actuated by axial forces of acceleration will not function properly at reentry because the forces produced by oscillation of the missile at reentry are not axial and continually vary in magnitude and direction.

It is an important object of this invention to provide a safety and arming system for use in a ground-to-ground missile which will successfully arm the missile at re-entry.

Another object of this invention is to provide a safety and arming system for use in a ground-to-ground missile which arm the missile warhead a constant time after reentry and before impact.

Another object of this invention is to provide a safety and arming system for use in a ground-to-ground missile which arms the missile warhead only after the missile has been launched, has traveled a constant time from the launch site, has re-entered the atmosphere, and has traveled for a constant time thereafter towards the target.

Briefly, the safety and arming system of this invention utilizes in combination a pair of clocks and a pair of G weights. The first G weight is actuated by missile acceleration and initiates timed rotation of one clock. This clock unlocks a pair of butterfly weights which are responsive to missile deceleration caused by air drag at re-entry. The butterfly weights in turn initiate operation of another clock which arms the missile warhead after some constant time interval elapses.

The specific nature of the invention, as well as other objects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

The drawing is a persective view of a safety and arming system constructed in accordance with this invention.

Referring now to the figure for a more complete understanding of the invention, there is shown a perspective "ice view of a preferred embodiment on my safety and arming system 10. System 10 is designed to be housed in the missile nose cone and comprises a pair of supporting plates 11 and 12. These plates are held apart as shown by spacing sleeves 14, 14a and 14b. Bolts 15, 15a and 15b secure the sleeves to the plates by means of nuts 17, 17a and 17!).

System 10 should be positioned in the missile so that sleeves 14, 14a and 14b are parallel to the major or longitudinal axis of the missile. Clock 18 is secured by adhesion, welding or bolts to the inner surface of plate 12 and provides a source of constant time. Preferably this clock is of the type known in the fuzing art as the T-3. This clock is manufactured by General Time Corporation of La Salle, Illinois, and is provided with a spring-biased arm 19 which can be manually cocked and which initiates timed rotation of a central shaft in the clock when released. As shown in the figure, arm 19 is held in a cocked position by G weight 31 and is released when the G weight moves from engagement with the arm.

Shaft 32 is designed to support the G weight 31 from the position shown in the figure to the position where the G weight no longer contacts arm 19. The G weight is urged into the position of locking arm 19 against release by coil spring 3201. In order to insure against any movement of the G weight 31 to a position where it would disengage from and thereby release arm 19, a launchlatch (not shown) may be employed to lock the weight in the position shown in the figure until a solenoid (not shown), energized by missile launch, withdraws the latch from looking engagement with the G weight. Such launch-latch and solenoid combinations are of course well known in the art and can be added to system 10 if greater safety is desired.

Shaft 35 is driven in timed rotation by clock 18 upon release of arm 19, as discussed above. Pinion 36 is fixed to the end of shaft 35 and meshes with gears 38 and 39. Both gears are rotatably mounted on plate 11. Cam 49 is fixed to gear 39 and has a cam surface 41 which enters rectangular slot 42 in one of the butterfly weights 43. Cam surface 41a has a radius less than that of surface 41 so that when surface 41a is rotated to a position opposite slot 42 it does not contact weight 43 and thusly releases this weight for pivotal movement.

Butterfly weights 43 and 44 are pivotally connected substantially centrally thereof to the leg 47 of the L-shaped support 48 by pins 49 and 59. Fixed to the ends of these weights are a pair of meshing gears 49a and Stia of the same size and containing the same number of teeth which rotate as a result of pivotal movement of the butterfly weights. Coil spring 51 has one end connected to rod 52 extending from leg 47 and the other end connected to weight 44 thereby urging the weight 44 to the position shown in the figure. At one of the free ends of weight 44 is pin 54 which holds arm 55 of clock 57 in the cocked position. Clock 57 is of the same construction as that of clock 18 hereinbefore referred to and described. Upon pivotal movement of weight 44, pin 54 disengages from arm 55 and releases the arm so that it initiates timed rotation of shaft 60 connected to internal gearing in the clock. Shaft 60 carries contacts 61 which complete the circuit to the missile warhead by rotating and engaging contacts 63.

It will be evident to those skilled in the art that rotative movement of the shaft 69 may also be used to turn rotary switches and thereby close the electrical circuit to the missile warhead. The shaft may also drive a rotor carrying one or more detonators from an out-of-line to an in-line position with respect to the explosive train.

Butterfly weights 43 and 44 are substantially the same size and shape and are interconnected by gears 49a and 50a. The centers of gravity and their axis of rotation are preferably in a plane perpendicular to the major axis of the missile. This axis is indicated by line AA. At re-entry, oscillation resulting from the missile attempting to properly align itself with its downward trajectory causes forces to develop in system 10 which are at substantially right angles to axis AA. Only the component of force parallel to axis AA acting through the centers of gravity of the weights in the direction indicated by arrow D will cause inward pivotal movement of these Weights such that pin 54 releases arm 55.

Forces produced by oscillation will be simultaneously experienced by both weights and at the instant of application will be in the same direction. Since weights 43 and 44 are locked together by gears 49a and 50a, the effect of forces acting at right angles, or substantially right angles, to axis AA will be canceled out because the gears will be forced to rotate in the same direction as a consequence of the weights tending to rotate in the same direction about their pivot points. The gears of course cannot rotate in the same direction since the weights are of the same size and shape, the resultant effect will be that the weights do not respond to these forces.

It will be apparent, however, that force components acting in the direction of arrow D through the center of gravity of each weight will cause gears 49a and 50a to rotate in opposite directions so as to permit the free ends 43a and 44a of the weights to move inwardly a distance suificient to allow pin 54 to release arm 55. Such force components are developed only as a result of missile deceleration produced by air drag on the missile as it reenters the atmosphere.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction and arrangement Within the scope of the invention as defined in the appended claim.

I claim as my invention:

In a safety and arming system for use in a missile, a first clock and a G weight locking said clock against rotative movement, said G weight being aligned in said system in such a manner that acceleration of the system produces movement of said G weight a sufficient amount to unlock said clock for rotative movement, a pair of butterfly weights, said weights being pivotally mounted approximately centrally thereof and having free ends which approach each other in response to deceleration forces produced by missile re-entry, a gear connected to each weight at the point of pivot, each gear meshing so that the force components which are substantially perpendicular to the missiles longitudinal axis are effectively canceled, while those parallel to the longitudinal axis cause said inward movement of the weights, a cam driven by said first clock positioned to engage and lock said pair of butterfly weights from pivotal movement, said pair of weights being unlocked when said first clock rotates the cam away from locking said pair of butterfly weights, a second clock means, an arm extending from said second clock means and normally engaging one of said pair of weights and locking said second clock against rotational movement until said butterfly weights are moved a predetermined distance inward in response to deceleration of said missile, said second clock arming the missile warhead.

References Cited in the file of this patent UNITED STATES PATENTS 2,789,508 Rove et al Apr. 23, 1957 2,801,589 Meek et a1 Aug. 6, 1957 2,984,184 Cetre May 16, 1961 2,996,009 Donahue et a1 Aug. 15, 1961 

